The present invention relates to vertebral osteosynthesis equipment.
A vertebral osteosynthesis equipment generally includes bony anchoring members, such as pedicular screws or lamar hooks, one or two linking rods, intended to be connected to these anchoring members and to be attached to the vertebrae by dint thereof, and parts for connecting this(these) linking rod(s) to these anchoring members. The equipment may also comprise length-adjustable crossbeams, which link transversally two parallel linking rods in order to hold said rods with respect to one another.
In an existing type of equipment, each anchoring member comprises a proximal threaded stud and a base portion intended for bony anchoring thereof. Each connecting part comprises a rounded section intended for surrounding a linking rod and two parallel drilled wings, these wings being intended for engaging onto said proximal threaded stud and for being clamped, using a nut screwed on the stud, against a bearing surface provided on said base portion. This clamping causes the clamping of said rounded section around the linking rod and thus ensures longitudinal immobilization of this rod with respect to the anchoring member. The anchoring members may be of “monoaxial” type, i.e. comprise a proximal threaded stud integral with the base portion, or may be of “polyaxial” type, i.e. comprise a proximal threaded stud articulated with respect to that base portion.
When installing the equipment, the anchoring members are placed, then extension pieces are engaged on the proximal studs of these anchoring members. The connecting parts, with the rod(s) engaged in their rounded portions, are then engaged on these extension pieces and run down along the latter until they rest on the proximal zones of the base portions of the anchoring members. The extension pieces are then withdrawn and the clamping nuts are placed.
To enable adequate correction of the position of the vertebrae, the linking rod(s) must be shaped into one or several planes. Such operation leads to successive trials and errors until adequate form is obtained. Successive insertions and retractions of the extension pieces and successive running down operations of the assemblies composed of connecting parts—linking rods along the latter, then withdrawing the extension pieces for placing the nuts, are then relatively tedious and time-consuming operations.
Moreover, there is always the risk of nut breaking loose from its installing instrument, and then, the necessity of retrieving this nut before placing it back on said this instrument; all this process contributes to make the implantation of the equipment longer and more complex.